The present invention pertains to stable liquid laundry detergent formulations comprising polycarboxylate builders.
The use of builders to improve the overall detergency effectiveness and the whitening power of liquid laundry detergent formulations is well known. Typically, builders have been used, among other things, as sequestering agents to remove metallic ions such as calcium or magnesium (or the xe2x80x9chardnessxe2x80x9d) from the washing fluid, to provide solubilization of water insoluble materials, to promote soil suspension, to retard soil redeposition and to provide alkalinity. Examples of liquid laundry detergent formulations are described in U.S. Pat. Nos. 6,034,045, 5,858,951, 5,575,004, 5,308,530, 4,663,071 and 3,719,647.
Polyphosphate compounds, such as tripolyphosphates and pyrophosphates, have been widely used as builders in detergent compositions, in part because of their ability in sequestering hardness ions. While the use of such phosphate compounds has been very effective, environmental concerns have mounted regarding their possible contribution to the growth of algae in lakes and streams and the resulting eutrophication of such bodies of water. This concern has caused significant legislative pressure to lower or discontinue use of phosphates in detergent compositions to control pollution.
Detergent manufacturers have looked to polycarboxylate polymers and copolymers as potential effective, non-phosphate detergent builders. For instance, U.S. Pat. Nos. 5,308,530, 4,663,071 and 3,719,647 disclose polycarboxylate builders for use with suitable surfactants in laundry detergent formulations. In U.S. Pat. No. 3,719,647, the polycarboxylate builder comprises a copolymer of a polyether and carboxylic acid, wherein the polyether component is made up of ethylene oxide units.
Often, a polycarboxylate may be unsuited for use as a liquid laundry detergent formulation builder, even when having excellent detergency effectiveness and whitening power. This is because the polycarboxylate is not readily compatible with anionic and non-ionic surfactants, i.e., does not exhibit acceptable phase stability. If a polymer is not readily compatible with these surfactants, phase separation in the liquid laundry detergent may result, thus requiring the addition of expensive hydrotropes for stabilization.
Accordingly, there is a need to identify liquid laundry detergent formulations comprising polycarboxylate builders that do not require the use of hydrotropes to be stable in liquid laundry detergents.
It has now been surprisingly discovered that liquid laundry detergent formulations comprising polycarboxylate builders and a certain dihydric glycol carrier solvent have an extremely broad range of phase stability. The dihydric glycol carrier solvent comprises 2-methyl-1,3-propanediol, sold as MPDiol(copyright) glycol by Lyondell Chemical Company.
It has also been surprisingly discovered that certain non-hydrophobically modified, acrylic/polyether comb-branched copolymers, wherein the polyether units contain moieties derived from at least two constituents selected from the group consisting of ethylene oxide, propylene oxide, and butylene oxide, are useful as builders, even without any 2-methyl-1,3-propanediol in laundry detergent formulations.
The non-hydrophobically modified, acrylic/polyether comb-branched polymers of the present invention exhibit surprisingly good anti-redeposition and stability properties when used in liquid laundry detergent formulations. Furthermore, it has also been surprisingly discovered that the non-hydrophobically modified, acrylic/polyether comb-branched copolymers of the present invention exhibit surprisingly good anti-redeposition and anti-encrustation properties when used in a solid laundry detergent formulation.
Minimally, liquid laundry detergent formulations made in accordance with the present invention comprise a surfactant (surface active agent), a polycarboxylate builder, water, and 2-methyl-1,3-propanediol solvent. Additionally, the liquid laundry detergent formulations of the present invention may also comprise ion exchangers, alkalis, anti-corrosion materials, anti-redeposition materials, optical brighteners, fragrances, dyes, fillers, chelating agents, enzymes, fabric whiteners and brighteners, sudsing control agents, bleaching agents, bleach precursors, buffering agents, soil removing agents, soil release agents, fabric softening agents, and opacifiers. Examples of liquid laundry detergent formulations and the manner in which they are made are described in U.S. Pat. Nos. 6,034,045, 5,858,951, 5,575,004, 5,308,530, 4,663,071 and 3,719,647, which are incorporated herein by reference.
The 2-methyl-1,3-propanediol is present in the liquid laundry detergent formulation in an amount effective to increase the phase stability of the liquid laundry detergent formulation relative to liquid laundry detergent formulations not containing the effective amount of the 2-methyl-1,3-propanediol. Preferably, the liquid laundry detergent formulations of the present invention comprise between about 0.1 to about 60 weight percent of a surfactant, about 0.1 to about 70 weight percent of a polycarboxylate builder, about 0.1 to 50 weight percent 2-methyl-1,3-propanediol and about 50 to about 99 weight percent water. More preferably, the liquid laundry detergent formulations of the present invention comprise between about 0.5 to about 30 weight percent of a surfactant, about 0.1 to about 40 weight percent of a polycarboxylate builder, about 0.1 to 40 weight percent 2-methyl-1,3-propanediol, and about 50 to about 99 weight percent water. Most preferably, the liquid laundry detergent formulations of the present invention comprise between about 5 to about 20 weight percent of a surfactant, about 0.1 to about 30 weight percent of a polycarboxylate builder, about 0.1 to 20 weight percent 2-methyl-1,3-propanediol, and about 50 to about 99 weight percent water. In each formulation, the sum of all weight percentages totals 100%, including, of course, the weight percentages of the aforementioned additional ingredients.
The 2-methyl-1,3-propanediol functions as carrier solvent or as a surfactant compatabilizer. 2-Methyl-1,3-propanediol is available commercially as MPDiol(copyright) glycol from Lyondell Chemical Company. In addition to the 2-methyl-1,3-propanediol, other carrier solvents may be used. Suitable examples of other carrier solvents include methanol, ethanol, propanol, isopropanol, 1,3-propanediol, ethylene glycol, glycerine, and 1,2-propanediol (propylene glycol).
The chemical nature of the surfactants, as well as the various optional components used in detergent compositions, are well known to those skilled in the art. Typical disclosures of these materials may be found in U.S. Pat. No. 4,663,071, which is incorporated herein by reference. It should be understood that the surfactant portion of the liquid laundry detergent formulation may comprise one surfactant or a blend of surfactants. The surfactants may include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants.
Any suitable polycarboxylate builder can be used. The polycarboxylate builder component can comprise one polycarboxylate builder, a mixture of polycarboxylate builders, or a mixture of one or more polycarboxylate builders with one or more non-polycarboxylate builders. Suitable polycarboxylate and non-polycarboxylate builders are well known in the art and can be found in various literature sources, such as U.S. Pat. Nos. 4,663,071, 5,308,530, 3,719,647, and 5,574,004, which are incorporated herein by reference.
A preferred polycarboxylate builder comprises a non-hydrophobically modified, acrylic/polyether comb-branched copolymer wherein the polyether portion comprises moieties derived from at least two constituents selected from the group consisting of ethylene oxide, propylene oxide and butylene oxide. By non-hydrophobically modified, it is meant that the polyether chain does not bear any hydrophobic end caps, i.e. a hydrocarbon having more than four carbon atoms, such as 2-ethylhexyl, lauryl, nonylphenyl, and the like. It should be noted that the preferred non-hydrophobically modified, acrylic/polyether comb-branched copolymer of the present invention is suitable for use as a builder or cobuilder in both liquid laundry detergent formulations and solid laundry detergent formulations such as powder laundry detergent formulations and tablet laundry detergent formulations. When used in liquid laundry detergent formulations, the preferred non-hydrophobically modified acrylic/polyether comb-branched copolymer of the present invention exhibits acceptable results even when used without any 2-methyl-1,3-propanediol.
The non-hydrophobically modified, acrylic/polyether comb-branched copolymer preferably has a molecular weight of 400 grams per mole to about 500,000 grams per mole, more preferably between about 600 grams per mole to about 400,000 grams per mole, and most preferably between about 1,000 grams per mole to about 100,000 grams per mole. The copolymer preferably has a mole ratio of acrylic monomer units to polyether units of about 1/99 to about 99/1, more preferably from about 1/1 to about 20/1, and most preferably from about 4/1 to about 20/1.
The comb-branched copolymer can be made by any suitable process for copolymerizing acrylic units with polyether units, as long as the resulting copolymer is non-hydrophobically modified and comprises polyether units containing moieties derived from at least two constituents selected from the group consisting of ethylene oxide, propylene oxide and butylene oxide. Preferably, the copolymer is formed by reacting a polyether polymer or macromonomer with an acrylic monomer or polyacrylic acid polymer. The process may be continuous, batch, or semi-batch. Following the copolymerization process, any relatively volatile unreacted monomers are generally stripped from the product.
More preferably, the comb-branched copolymer is made according to a process selected from the group consisting of (i) copolymerizing an unsaturated macromonomer with at least one ethylenically unsaturated comonomer selected from the group consisting of carboxylic acids, carboxylic acid salts, hydroxyalkyl esters of carboxylic acids, and carboxylic acid anhydrides, and (ii) reacting a carboxylic acid polymer and a polyether prepared by polymerizing a C2-C4 epoxide, wherein the carboxylic acid polymer and the polyether are reacted under conditions effective to achieve partial cleavage of the polyether and esterification of the polyether and cleavage products thereof by the carboxylic acid polymer.
The preferred polyether polymer or macromonomer preferably comprises ethylene oxide and propylene oxide and has a molecular weight of about 300 grams per mole to about 100,000 grams per mole, more preferably between about 500 grams per mole to about 75,000 grams per mole, and most preferably between about 1,000 grams per mole to about 10,000 grams per mole. All molecular weights are number average molecular weights unless stated otherwise. Preferably, the ratio of propylene oxide (PO) to ethylene oxide (EO) of the polyether polymer or polyether macromonomer is preferably between about 99/1 to about 1/99, more preferably between about 80/20 to about 1/99, and most preferably between about 60/40 to about 1/99 by weight.
A preferred process for making the copolymer comprises: (a) forming a monomer stream, an initiator stream, and an optional chain transfer agent stream; (b) polymerizing the. streams in a reaction zone at a temperature within the range of about xe2x88x9220xc2x0 C. to about 150xc2x0 C.; and (c) withdrawing a polymer stream from the reaction zone. This process is described in more detail in copending U.S. patent application Ser. No. 09/358,009, filed Jul. 21, 1999, which is incorporated herein by reference.
The monomer stream contains an acrylic monomer and a polyether macromonomer. Suitable acrylic monomers are derived from acrylic acid and methacrylic acid. Preferred acrylic monomers include acrylic acid, methacrylic acid, their ammonium and alkali metal salts, their C1 to C10 alkyl and C6 to C12 aryl esters, and their amides. Acrylic acid, methacrylic acid, ammonium acrylate, ammonium methacrylate, sodium acrylate, sodium methacrylate, potassium acrylate, and potassium methacrylate are preferred. Most preferred are acrylic acid and methacrylic acid.
Suitable polyether macromonomers have a polyether chain and a single carbon-carbon double bond, which can be located either terminally or within the polyether chain. Examples include polyether monoacrylates, polyether monomethacrylates, polyether monoallyl ethers, polyether monomaleates, and polyether monofumarates. Further examples include the reaction product of a hydroxyl-functional polyether with isocyanatoalkyl(meth)acrylates such as isocyanatoethylacrylate, and with ethylenically unsaturated aryl isocyanates such as TMI. The polyether of the macromonomer is an alkylene oxide polymer having a number average molecular weight within the range of about 500 to about 10,000. Suitable alkylene oxides include ethylene oxide, propylene oxide, butylene oxide, and the like, and mixtures thereof. The polyether macromonomers preferably have hydroxyl functionality from 0 to 5. They can be either linear or branched polymers, homopolymers or copolymers, random or block copolymers, diblock or multiple-block copolymers.
Examples of polyether macromonomers are poly(propylene glycol) acrylates or methacrylates, poly(ethylene glycol) acrylates or methacrylates, poly(ethylene glycol) methyl ether acrylates or methacrylates, acrylates or methacrylates of an oxyethylene and oxypropylene block or random copolymer, poly(propylene glycol) allyl ether, poly(ethylene glycol) allyl ether, poly(propylene glycol) monomaleate, and the like, and mixtures thereof. Preferred polyether macromonomers are poly(propylene glycol) acrylates or methacrylates, poly(ethylene glycol) acrylates or methacrylates, acrylates or methacrylates of an oxyethylene and oxypropylene block and/or random copolymer. More preferred are acrylates or methacrylates of an oxyethylene and oxypropylene block and/or random copolymer.
The ratio of acrylic monomer to polyether macromonomer is determined by many factors within the skilled person""s discretion, including the required physical properties of the comb-branched copolymer, the selection of the acrylic monomer, and the properties of the polyether macromonomer. The ratio generally is within the range from 1/99 to 99/1 by weight. The preferred range is from 5/95 to 75/25.
In one embodiment, t he macromonomer is made by (a) oxyalkylating an initiator molecule selected from the group consisting of hydroxyalkyl acrylates, hydroxyalkyl methacrylates, and monounsaturated monocarboxylic acids with an alkylene oxide in the presence of an effective amount of a double metal cyanide complex catalyst under conditions effective to form a well-defined unsaturated macromonomer having a terminal hydroxyl functionality and not more than substantially one initiator molecule per unsaturated macromonomer molecule. This method is described in substantial detail in U.S. Pat. No. 6,034,208, which is incorporated herein by reference. Also, the macromonomer described in U.S. Pat. No.6,034,208 in addition to being reacted in the manner described in the preferred continuous process described herein, can be reacted with the comonomer in the manner described in U.S. Pat. No. 6,034,208.
Optionally, the monomer stream contains a third monomer. The third monomer is preferably selected from vinyl aromatics, vinyl halides, vinyl ethers, vinyl esters, vinyl pyrrolidinones, onjugated dienes, unsaturated sulfonic acids, unsaturated phosphonic acids, and the like, and mixtures thereof. The amount of third monomer used depends on the required physical properties of the comb-branched copolymer product, but is preferably less than 50% by weight of the total amount of monomers.
Optionally, the monomer stream also includes a solvent. The solvent is used to dissolve the monomer, to assist heat transfer of the polymerization, or to reduce the viscosity of the final product. The solvent is preferably selected from water, alcohols, ethers, esters, ketones, aliphatic hydrocarbons, aromatic hydrocarbons, halides, and the like, and mixtures thereof. Selections of solvent type and amount are determined by the polymerization conditions including reaction temperature. Water and alcohols, such as methanol, ethanol, and isopropanol are preferred.
The initiator stream contains a free radial initiator. The initiator is preferably selected from persulfates, hydrogen peroxide, organic peroxides and hydroperoxides, azo compounds, and redox initiators such as hydrogen peroxide plus ferrous ion. Persulfates, such as ammonium and potassium persulfate, are preferred.
Optionally, the initiator stream contains a solvent. The solvent is used to dissolve or dilute the initiator, to control the polymerization rate, or to aid heat or mass transfer of the polymerization. Selections of solvent type and amount are determined by the nature of the initiator and the polymerization conditions. Water and alcohols such as methanol, ethanol, and isopropanol are preferred when persulfate is used as the initiator.
The monomer and initiator streams optionally include a chain transfer agent. Suitable chain transfer agents include alkyliodides and bromides, branched lower alcohols such as isopropanol, alkyl amines, alkyl sulfides, alkyl disulfides, carbon tetrahalides, allyl ethers, and mercaptans. Mercaptans, such as dodecyl mercaptan, butyl mercaptan, mercaptoacetic and mercaptopropionic acids, are preferred.
Under some conditions, it is preferred to add the chain transfer agent in a separate stream. This is particularly desirable when the chain transfer agent causes decomposition of the initiator or polymerization of the monomer once it is mixed with those components. This is particularly important in a large, commercial scale because these reactions can cause safety problems.
Optionally, the chain transfer agent stream contains a solvent that is used to dissolve or dilute the chain transfer agent. Suitable solvents include water, alcohols, ethers, esters, ketones, aliphatic and aromatic hydrocarbons, halides, and the like, and mixtures thereof. Selections of solvent type and amount are determined by the nature of the chain transfer agent and the polymerization conditions. Water and alcohols, such as methanol, ethanol, and isopropanol, are preferred.
The monomer stream, initiator stream, and optional chain transfer agent stream are polymerized in a reaction zone. The reaction temperature is preferably kept essentially constant during the polymerization. The temperature is determined by a combination of factors including the desired molecular weight of the comb-branched polymer product, the initiator type and concentration, the monomer type and concentration, and the solvent used. The reaction is performed at a temperature within the range of about xe2x88x9220xc2x0 C. to about 150xc2x0 C., preferably, within the range of about 20xc2x0 C. to about 90xc2x0 C. Most preferred is the range of about 40xc2x0 C. to about 60xc2x0 C.
The addition rate of each stream depends on the desired concentration of each component, the size and shape of the reaction zone, the reaction temperature, and many other considerations. In general, the streams flow into the reaction zone at rates that keep the initiator concentration within the range of about 0.01% to about 1% by weight, and the chain transfer agent concentration within the range of about 0.1% to about 1.5% by weight.
The reaction zone is where the polymerization takes place. It can be in the form of a tank reactor, a tubular reactor, or any other desirably shaped reactor. The reaction zone is preferably equipped with a mixer, a heat transfer device, an inert gas source, and any other suitable equipment.
As the streams are polymerized in the reaction zone, a polymer stream is withdrawn. The flow rate of the polymer stream is such that the reaction zone is mass-balanced, meaning that the amount of material that flows into the reaction zone equals to the amount of material withdrawn from the reaction zone. The polymer stream is then collected.
The comb-branched copolymer may also be made according to a multiple-zone process. A multiple-zone process is similar to the process discussed above except that more than one reaction zone is used. In a multiple-zone process, a first polymer stream is withdrawn from a first reaction zone and transferred into a second reaction zone where the polymerization continues. A second polymer stream is withdrawn from the second reaction zone. More than two reaction zones can be used if desirable. The reaction temperature in the second reaction zone can be the same as or different from the first reaction zone. A multiple-zone process can enhance monomer conversion and increase efficiency of the process. Usually, in the first polymer stream, the monomer conversion is within the range of about 65% to 85% by weight. The second reaction zone preferably brings the monomer conversion to 90% or greater.
In a second preferred process, the comb-branched copolymer of the present invention for use with the laundry detergent formulations can be made by reacting (a) a carboxylic acid polymer prepared by polymerizing a polymerizable acid monomer containing at least one ethylenically unsaturated group in conjugation with a carboxyl group selected from the group consisting of carboxylic acid, carboxylic anhydride and carboxylic ester groups, and (b) a polyether prepared by polymerizing a C2-C4 epoxide, wherein (a) and (b) are reacted under conditions effective to achieve partial cleavage of the polyether and esterification of the polyether and cleavage products thereof by the carboxylic acid polymer. This method is described in substantial detail in U.S. Pat. No. 5,614,017, which is incorporated herein by reference.